Electromigration evaluation methodology with consideration of both self-heating and heat sink thermal effects

ABSTRACT

An electromigration (EM) sign-off methodology that analyzes an integrated circuit design layout to identify heat sensitive structures, self-heating effects, heat generating structures, and heat dissipating structures. The EM sign-off methodology includes adjustments of an evaluation temperature for a heat sensitive structure by calculating the effects of self-heating within the temperature sensitive structure as well as additional heating and/or cooling as a function of thermal coupling to surrounding heat generating structures and/or heat sink elements located within a defined thermal coupling volume or range.

PRIORITY CLAIM

The present application is a continuation of U.S. patent application Ser. No. 16/425,862, filed May 29, 2019, which claims priority to U.S. Prov. Pat. Appl. No. 62/720,475, filed Aug. 21, 2018, the contents of which are incorporated herein by reference, in their entireties.

BACKGROUND

Current passing through conductive lines induces electromigration (EM), i.e., the movement of the metal atoms resulting from momentum transfer between the electrons passing through the conductive lines and the metal atoms comprising the conductive lines. Over time, EM causes the formation of hillocks (accumulation of excess metal) and/or voids (depletion of initial metal) in the wire which, in turn, tends to result in short circuits (hillocks) or open circuits (voids).

A mean time to failure (MTTF) for conductive lines caused by EM is estimated by taking into consideration a number of operative factors including, for example, the sizing(s) of the conductive lines, the composition of the conductive lines, the microstructure of the conductive lines, the current density carried by the conductive lines, the duty cycle(s) over which the current is applied to the conductive lines, and the operating temperature(s) of the conductive lines. EM evaluation, analysis, and signoff methodologies applied to a particular integrated circuit design attempt to take at least some of the operative factors into consideration in order to provide a reasonable and prudent estimate regarding the lifetime of semiconductor devices manufactured using the integrated circuit design to avoid premature failure of the semiconductor devices.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the following detailed description when read with the accompanying figures. It is noted that, in accordance with the standard practice in the industry, various features are not drawn to scale. In fact, the dimensions of the various features may be arbitrarily increased or reduced for clarity of discussion.

FIG. 1 is a schematic view of a process of electromigration (EM) within a metal wire.

FIG. 2 is a schematic view of thermal coupling between components in some embodiments.

FIG. 3 is a schematic view of an EM tool useful in the operation of an EM sign-off methodology in accordance with some embodiments.

FIG. 4 is a plan view of an active region (AR) (in some embodiments the active region is an oxide defined (OD) region in which transistor and other functional semiconductor device elements are formed) in accordance with some embodiments.

FIGS. 5A and 5B are cross-sectional views of evaluations of thermal coupling between components in some embodiments.

FIG. 6A is a flow chart of a method for conducting a self-heating aware EM evaluation in accordance with some embodiments.

FIG. 6B is a flow chart of a method for conducting a heat sink aware EM evaluation in accordance with some embodiments.

FIG. 7A is a plan view of evaluations of thermal coupling between target and heat generating components in accordance with some embodiments.

FIG. 7B is a plan views of evaluations of thermal coupling between target and heat sink components in accordance with some embodiments.

FIG. 8 is a cross-sectional view of evaluations of thermal coupling between front end (FE) and back end (BE) components in accordance with some embodiments.

FIGS. 9A-D are perspective views of results of an EM evaluation in accordance with some embodiments.

FIG. 10 is a table including plan views of a heat sink aware EM evaluation in accordance with some embodiments.

FIG. 11 is a schematic view of an electronic process control (EPC) system useful in the operation of an EM sign-off methodology in accordance with some embodiments.

DETAILED DESCRIPTION

This description of the exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. The following disclosure provides many different embodiments, or examples, for implementing different features of the provided subject matter. Specific examples of components, values, operations, materials, arrangements, or the like, are described below to simplify the present disclosure. These are, of course, merely examples and are not intended to be limiting. Other components, values, operations, materials, arrangements, or the like, are contemplated. For example, the formation of a first feature over or on a second feature in the description that follows may include embodiments in which the first and second features are formed in direct contact, and may also include embodiments in which additional features may be formed between the first and second features, such that the first and second features may not be in direct contact. In addition, the present disclosure may repeat reference numerals and/or letters in the various examples. This repetition is for the purpose of simplicity and clarity and does not in itself dictate a relationship between the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,” “above,” “upper” and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the Figures. The spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the Figures. The apparatus may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein may likewise be interpreted accordingly.

Semiconductor devices tend to increase in temperature during use as a result of self-heating effects (SHE). These SHE limit both the performance capability and the operational lifetime of the affected semiconductor devices. For example, self-heating effects in semiconductor devices such as fin field effect transistors (FinFETs) will tend to reduce device performance and reliability.

Accordingly, some FinFET integrated circuit designs utilize the conductive lines and interconnecting vias as heat dissipation conduits for controlling the temperature of the active structures. This technique for dissipating heat; however, increases the operating temperature of the conductive lines. The heating from other active elements, when coupled with inherent current/resistance (IR) heating (also referred to as ohmic or joule heating) of conductive lines, increases the risk of accelerated EM-related failures. Device designers seek to address the risk of increased EM resulting from SHE in the conductive lines to some degree by modifying the integrated circuit design and/or operational parameters, but such design compensations tend to reduce the density, reduce the performance, and/or increase the size of the resulting semiconductor device.

FinFET processes and the resulting semiconductor devices tend to provide power, performance, and area benefits over planar semiconductor devices. The FinFET integrated circuit designs; however, tend to exhibit greater local current densities which, in turn, lead to greater concern for EM failures in the conductive lines comprising the signal and power rail interconnections within the FinFET semiconductor devices.

In some instances, a FinFET semiconductor device includes a substrate in which is formed an active region in which a source and drain are formed, a guard ring, a plurality of conductive line layers separated by layers of interlayer dielectric (ILD) material(s), and vias formed through the ILD materials to establish electrical connections to and between the conductive line layers. Depending on the particular integrated circuit design, heat generated within the active regions of the semiconductor device will reach portions of the conductive line layers that are within the active region impact range and, to some extent, through the vias connecting the conductive lines to the active region.

Because the heat dissipation paths available in FinFET integrated circuit designs are limited by the fin structure, there will be regions and/or structures within the integrated circuit design in which the SHE result in increased operating temperatures that will increase the likelihood of accelerated EM degradation. In some particularly heat sensitive integrated circuit designs, a temperature increase of as little as 10° C. is capable of increasing the EM degradation by 50%. The concerns regarding SHE tend to increase for the reduced structural dimensions associated with more advanced processes and/or high-speed/high-performance integrated circuit designs.

EM occurs when electrical current runs through a conductive line and the electrons transfer a portion of their momentum to the atoms, thereby tending to urge the atoms in the direction of the electron flow. As in FIG. 1, conductive line segment 100 includes a conductive line 102 including a plurality of metal atoms 104, selected from a group of metals including, e.g., aluminum (Al), copper (Cu), titanium (Ti), tantalum (Ta), tungsten (W), platinum (Pt), cobalt (Co) and, in some embodiments, one or more alloying metals or other elements including nickel (Ni), nitrogen (N), and silicon (Si), that have been patterned to form a conductive path for the electrons 106 moving between the cathode and the anode. The repeated transfers of momentum from the electrons 106 to the metal atoms 104 during operation of the semiconductor device will gradually shift the metal atoms from their original positions, thereby increasing the non-uniformity of the conductive line 102.

In those regions of the conductive line in which the movement of the metal atoms 104 reduces the cross-section of the conductive line 102, the current density will increase and further exacerbate both the SHE and EM in the thinned region(s). Conductive lines 102 incorporating such thinned regions will exhibit increased resistance and will typically lead to reduced performance and, eventually, a void or an open circuit. Conversely, in those regions of the conductive line 102 in which the movement of the metal atoms 104 increases the cross-section of the conductive line 102, the thickened regions, e.g., hillocks, will tend to stress the surrounding materials and eventually compromise the structural integrity of the surrounding materials and/or create short circuit to an adjacent conductive line or other conductor.

To help reduce or eliminate EM-induced failures, the design rules associated with the manufacturing process will include EM rules to limit the average current density through a conductive line and to take into consideration the temperature of the conductive lines during the anticipated operation of the semiconductor device. Integrated circuit designs that pass all of the applicable EM rules are approved for EM signoff and tape-out.

In advanced FinFET processes, the SHE will increase the temperature of the transistor structure by a particular amount ΔT. At least a portion of the SHE that produces the ΔT will, in turn, be transferred to the conductive lines through direct contact with the transistor and via conduction through intervening materials, e.g., ILD materials/layers. In addition to the SHE associated with the FinFET structure, in some embodiments other high-resistance elements (Hi-R) present on the semiconductor device will also contribute to heating the conductive lines.

EM evaluation methodologies which do not identify and compensate for the increased operating temperature of the conductive lines resulting from or induced by thermal coupling to SHE elements within the semiconductor device have an increased risk of underestimating the conductive line operating temperature. Underestimating the conductive line operating temperature will, in turn, produce an EM evaluation result that is overly optimistic, will tend to overestimate the average lifetime of semiconductor devices manufactured to that design, and result in premature field failures of the affected semiconductor devices.

In order to improve EM evaluation methodologies, the EM evaluation should identify and consider those portions of an integrated circuit design in which SHE are expected to increase the operating temperature of at least a portion of a conductive line.

In some embodiments, a self-heating aware EM evaluation methodology will include using equation-based device temperature calculations; using a pseudo-3D thermal model for estimating the device-to-metal thermal coupling range(s) and effect(s) and generating an adjusted (or nominal) conductive line temperature; and conducting an EM confirmation check at the adjusted metal temperature to compensate for the SHE and improve the accuracy of the EM evaluation.

In some embodiments, in comparison with other EM evaluation methodologies, the self-heating aware EM evaluation methodology will provide more accurate local temperature calculations inside the integrated circuit design; more accurate thermal-aware EM evaluation results during the design phase; a reduced risk of premature product failure; reduced simulation runtime using equation-based device temperature calculations; and reduced EM emulation runtime using pseudo-3D thermal models rather than full 3-D thermal modeling.

In some embodiments, the self-heating-aware EM evaluation considers various thermal effects. In embodiments according to FIG. 2, three thermal effects are considered during the EM evaluation including, FinFET device self-heating; Hi-R device self-heating; and conductive line self-heating. In FIG. 2, a semiconductor structure 200 includes both a FinFET structure 202 and a Hi-R structure 204, both of which are embedded in an ILD structure 208 and which will generate heat during semiconductor device operation. A portion of the heat generated in FinFET structure 202 and Hi-R structure 204 will, in turn, be transferred to conductive line 206 via thermal coupling through the intermediate materials (not shown). In addition to the heat transferred from FinFET structure 202 and Hi-R structure 204, conductive line 206 will also experience some degree of self-heating as a function of the electrical current being transmitted by the conductive line. In some embodiments, the cumulative thermal effects of these three heat sources are then used to calculate an adjusted metal temperature that will be used for the EM evaluation.

In some embodiments according to FIG. 3, EM tool 300 includes a database 302 or other data storage device for storing design data corresponding to an integrated circuit layout, the design data then being used to generate a simulated design layout 304. The simulated design layout 304 is then used in combination with device temperature equations retrieved from a memory 306 to calculate 308 an anticipated increase in temperature ΔT for at least a portion of the heat generating devices identified in the simulated design layout, e.g., FinFET and Hi-R structures.

In some embodiments, the ΔT for FinFET structures is calculated using the device temperature equation Eq. 1: ΔT=R _(THC)×finger_effect×fin_effect×Power_(per fin·per finger)  [Eq. 1] In some embodiments, the relevant values and/or parameters included in the device temperature equation are provided by the foundry, incorporated in the applicable design rules, or extracted from the integrated circuit layout and include:

-   -   R_(THC): thermal resistance value (typically provided by         foundry).     -   fin number: determined from integrated circuit layout     -   finger number: determined from integrated circuit layout power         per fin per finger (watt) (typically provided by foundry)         finger-effect=finger number     -   fin-effect=fin number

In some embodiments, the device temperature equation is provided as part of the design tools provided by a semiconductor device foundry including, for example, a Simulation Program with Integrated Circuit Emphasis (SPICE) model corresponding to a particular manufacturing process.

In some embodiments, calculating the ΔTA for an active region is a function of the individual ΔT calculations for each of the structures incorporated within the particular active region. In some embodiments according to FIG. 4, for example, the ΔT_(AR) for active region active region structure 400 will be a function of ΔT calculations for a first polysilicon over diffusion edge (PODE) structure 404, a first conductor M1 406, a second conductor M2 408, a third conductor M3 410, and a second PODE structure 412 that are formed over a diffused region 402. This function is represented by Eq. 2 as presented below. ΔT _(OD) =f(ΔT _(PODE1) ,ΔT _(M1) ,ΔT _(M2) ,ΔT _(M3) ,ΔT _(PODE2))  [Eq. 2] In some embodiments, this cumulative ΔT_(OD) will then be used in subsequent calculations for evaluating the magnitude of thermal coupling between this active region and proximate heat sensitive structures, e.g., conductive lines.

Using a pseudo-3-D thermal model retrieved from memory 310, the EM tool 300 then calculates the anticipated increase in temperature ΔT for both conductive lines 312 and Hi-R structures 314 identified in the integrated circuit layout as a result of self-heating. The EM tool 300 then uses the ΔT data for the heat sensitive structures and proximate heat generating structures to calculate an adjusted operating temperature T_(E) for the temperature sensitive structures, e.g., conductive lines, during operation of a semiconductor device according to the integrated circuit layout.

In some embodiments, the pseudo-3-D thermal model will incorporate a number of coefficients, e.g., a, b, c, d, that will be specific to each of the materials and/or layers incorporated in the integrated circuit design under analysis and to the particular manufacturing process that will be used to produce semiconductor devices according to the integrated circuit design. In some embodiments, the ΔT for a heat sensitive structure, e.g., a conductive line, will be a function of both self-heating of the heat sensitive structure and the thermal contribution(s) from other heat generating structures proximate the heat sensitive structure. In some embodiments, the ΔT for a conductive line, for example, will be calculated according to Eq. 3 provided below: ΔT _(Con) =ΔT _(rms) +f(a,b,ΔT _(ch) ,c,d,ΔT _(Hi-R) ,ΔT _(other_devices), . . . )  [Eq. 3] In some embodiments, the relevant values and/or parameters included in the ΔT_(Metal) equation are provided by the foundry, incorporated in the applicable design rules, or extracted from the integrated circuit layout and include:

ΔT_(rms): current-induced metal heating

ΔT_(ch): FinFET device self-heating

ΔT_(Hi-R): Hi-R device self-heating

ΔT_(other_devices): Device self-heating from other devices

For the purposes of the ΔT_(Con) calculation according to Eq. 3, other devices will include, for example, bipolar junction transistors (BJT), diodes, and resistors that are thermally coupled to the conductive line under analysis.

The thermal coefficients a, b, c, and d are provided for each layer and/or material and reflect:

-   -   a=a derating coefficient (or de-rating coefficient) value         reflecting operation at less than maximum capacity     -   b=a function of ΔT_(rms) and ΔT_(ch) [f (ΔT_(rms), ΔT_(ch))]     -   c=a layer effect associated with the layer/material     -   d=a temperature profile associated with the layer/material

EM tool 300 then runs an EM analysis 316 using the adjusted T_(E) for the heat sensitive structures, e.g., conductive lines, to provide a more accurate analysis of the anticipated performance of the semiconductor device. In some embodiments, the EM tool will generate a tape out data file 318 corresponding to an integrated circuit layout that passes the EM analysis.

In some embodiments, the range over which thermal coupling is expected to occur between a heat generating structure and the heat sensitive structure, i.e., the impact range or thermal coupling range, is defined by a horizontal distance, i.e., the impact range or thermal coupling range, from the associated heat generating structure. In some embodiments according to FIG. 5A, a semiconductor device 500 includes a number of heat sensitive structures, e.g., conductive layers including, e.g., conductive line Ma 504, conductive line Mb 506, conductive line Mc 508, and conductive line Md 508, as well as two heat generating structures, i.e., active region 502 and Hi-R structure 512, arranged within dielectric and/or semiconducting material(s) 518. With respect to the structure 512, the Hi-R impact range 514 is set at A μm, while for the active region 502, the active region impact range 516 is set at B μm. The Hi-R and active region impact ranges are then projected vertically through the structure 500 to define both a Hi-R impact area and an active region impact area.

The ΔT_(Con) calculations for the heat sensitive structures according to Eq. 3 include a contribution based on the location of the conductive lines 504, 506, 508, 510 with respect to the Hi-R impact area and an active region impact area. In some embodiments according to FIG. 5A for example, the ΔT_(Con) for conductive line 504 will include thermal contributions from both the active region impact area and the Hi-R impact area, the ΔT_(Con) for conductive line 506 will not include a thermal contribution from either the active region impact area or the Hi-R impact area, the ΔT_(Con) for conductive line 508 will include a thermal contribution from only the active region impact area, and conductive line 510 will include a thermal contribution from only the Hi-R impact area.

In some embodiments, the range over which thermal coupling is expected to occur between a heat generating structure and the heat sensitive structure, i.e., the impact range, is defined by a distance extending from the associated heat generating structure. In some embodiments according to FIG. 5B, a semiconductor device 500 includes a number of heat sensitive structures, i.e., conductive line Ma 504, conductive line Mb 506, conductive line Mc 508, and conductive line Md 508, as well as two heat generating structures, i.e., active region 502 and Hi-R structure 512, arranged within dielectric and/or semiconducting material(s) 518. With respect to the structure 512, the Hi-R impact range 514 is set at A μm, while for the active region 502, the active region impact range 516 is set at B μm. The Hi-R and active region impact ranges are then rotated through the structure 500 to define both a Hi-R impact area and an active region impact area.

The ΔT_(Con) calculations for the heat sensitive structures according to Eq. 3 include a contribution based on the location of the conductive lines 504, 506, 508, 510 with respect to the Hi-R impact area and an active region impact area. In embodiments according to FIG. 5B for example, the ΔT_(Con) for conductive line 504 includes thermal contributions from both the active region impact area and the Hi-R impact area, the ΔT_(Con) for conductive line 506 does not include a thermal contribution from either the active region impact area or the Hi-R impact area, the ΔT_(Con) for conductive line 508 does not include a thermal contribution from either the active region impact area or the Hi-R impact area, and conductive line 510 includes a thermal contribution from only the Hi-R impact area.

In some embodiments according to FIG. 5A and/or FIG. 5B, the impact areas associated with two or more heat generating structures overlap, at least in part, to define a combined impact area.

FIG. 6A is a flowchart of a method 600 for improving the accuracy of EM evaluations conducted in connection with integrated circuit design by taking into account the degrading effects of increasing temperatures resulting from heat generating structures, i.e., structures that are projected to have an operating temperature above that of temperature sensitive structures that are situated within a heating impact area (an area over which thermal coupling is known or expected) that is associated with a particular heat generating structure. Evaluating the SHE of heat generating structures will, in some embodiments, suggest that the performance and/or lifetime of the heat sensitive structures will be degraded as a result of the proximity and operating temperature of the heat generating structure(s). By recognizing and compensating for the additional heat emanating from the heat generating structures, the EM evaluation according to some embodiments will provide a more pessimistic and more accurate estimate of the anticipated performance of the semiconductor device, thereby increasing the likelihood that the semiconductor devices will meet or exceed customer expectations.

In some embodiments of methods according to FIG. 6A, in operation 602, one or more temperature sensitive structures (TSS), e.g., transistors, conductive lines, and other structures for which an increased operating temperature will degrade performance and/or lifetime, are identified during a structural and/or operational review of an integrated circuit design layout that is under evaluation. In operation 604, proximate structures, e.g., surrounding and/or adjacent the temperature sensitive structure are evaluated for identification as heat generating structures (HGS). In order to be identified as a heat generating structure, i.e., a proximate structure will exhibit at least the properties of 1) an operating temperature that meets or exceeds a predetermined temperature level above the anticipated operating temperature of the temperature sensitive structure and 2) a location within the impact area defined by the temperature sensitive structure (or by the heat generating structure) that allows for thermal coupling between the heat generating structure and the temperature sensitive structure. Proximate structures having or exhibiting an operating temperature and location sufficient to meet the noted properties are then identified as heat generating structures.

Operation 606 involves a query regarding the extent to which the proximate structure(s) (PSs) has/have been successfully evaluated for potential identification as a heat generating structure. If fewer than all of the proximate structures have been evaluated, method 600 branches from operation 606 to operation 608 in order to identify the next proximate structure for evaluation as a heat generating structure and return to operation 604 for evaluation of the next proximate structure. When all of the proximate structures have been evaluated for possible identification as heat generating structures, method 600 branches to operation 610 for calculating the ΔT contribution to the operating temperature of the temperature sensitive structure from each of the identified temperature sensitive structures.

Operation 612 involves a query regarding the extent to which the temperature sensitive structures (TSSs) within the integrated circuit design have been successfully evaluated for potential identification as a heat generating structure. If fewer than all of the temperature sensitive structures on the integrated circuit design have been identified, method 600 operation branches from operation 612 to operation 613. During operation 613, the next temperature sensitive structure is identified on the integrated circuit design. The identification in operation 613 is then returned to operation 604 for identification of heat generating structures proximate the next temperature sensitive structure.

During optional operation 614, the effect of proximate heat sink elements, e.g., surrounding and/or adjacent, the temperature sensitive structure(s) is evaluated according to the method detailed in FIG. 6B, in order to provide a more precise adjusted temperature that takes into account both the heating and cooling effects of structures proximate the temperature sensitive structures. In operation 614, the proximate structures are evaluated for identification as heat sink elements (HSE). In order to be identified as a heat sink element a proximate structure will exhibit at least the properties of 1) an operating temperature that meets or exceeds a predetermined temperature difference below the anticipated operating temperature of the temperature sensitive structure and 2) a location within the impact area defined by the temperature sensitive structure (or by the heat sink element) that allows for thermal coupling between the proximate heat sink element and the temperature sensitive structure. Proximate structures having or exhibiting an operating temperature and location sufficient to meet the noted properties are then identified as heat sink elements.

In operation 616, the adjusted temperature T′_(H), which takes into account heating effects, or the fully adjusted temperature T″, which takes into account both heating and cooling effects with regard to the temperature sensitive structure is used in running an EM evaluation to determine whether or not the integrated circuit design layout under evaluation satisfies the lifetime and performance goals for the particular design. For an integrated circuit design layout that passes the EM evaluation of operation 616, in some embodiments, a tape out data file corresponding to the passing integrated circuit design layout is generated in optional operation 618. For those integrated circuit design layouts for which a tape out data file is generated, the tape out data file will be used to manufacture a semiconductor device according to the passing integrated circuit design layout in optional operation 620.

FIG. 6B is a flowchart of a method 600′ for improving the accuracy of EM evaluations conducted in connection with integrated circuit design by taking into account the temperature modulating effects of heat sink elements (HSE), i.e., elements or structures that are projected to have an operating temperature below that of proximate heat generating structures and/or the temperature sensitive structures. The consideration of the effects of heat sink structures will, in some embodiments, help compensate for thermal coupling between the heat sensitive structures and heat generating structures and/or SHE of the heat sensitive structures, thereby providing a lower and more accurate estimate of the operating temperatures of the heat sensitive structure and improving the accuracy of subsequent EM evaluations.

In embodiments of methods according to FIG. 6B, in operation 602, one or more temperature sensitive structures (TSS), e.g., transistors, conductive lines, and other structures for which an increased operating temperature will degrade performance and/or lifetime, are identified during a structural and/or operational review of an integrated circuit design layout that is under evaluation. In operation 604′, structures proximate, e.g., surrounding and/or adjacent, the temperature sensitive structure are evaluated for possible identification as heat sink elements (HSE). In order to be identified as a heat sink element, a proximate structure will exhibit at least the properties of 1) an operating temperature that is below, by a predetermined temperature level, the anticipated operating temperature of the temperature sensitive structures and 2) a physical proximity that allows for thermal coupling between the proximate heat sink element and the temperature sensitive structure. Proximate structures having or exhibiting an operating temperature and location sufficient to meet the noted properties are then identified as heat sink elements.

Operation 606 involves a query regarding to the extent to which the proximate structure(s) has/have been successfully evaluated for potential identification as a heat sink elements. If fewer than all of the proximate structures have been evaluated, method 600 branches from operation 606 to operation 608 in order to identify the next proximate structure for evaluation as a heat sink element and return to operation 604′ for evaluation of the next proximate structure. When all of the proximate structures have been evaluated for possible identification as heat generating structures, method 600 branches to operation 610 for calculating the ΔT contribution to the operating temperature of the temperature sensitive structure from each of the identified temperature sensitive structures.

Operation 612 involves a query regarding to the extent to which the temperature sensitive structures within the integrated circuit design have been successfully evaluated for potential identification as a heat generating structure. If fewer than all of the temperature sensitive structures on the integrated circuit design have been identified, method 600 operation branches from operation 612 to operation 613. During operation 613, the next temperature sensitive structure is identified on the integrated circuit design. The identification in operation 613 is then returned to operation 604′ for identification of heat elements proximate the next temperature sensitive structure.

During optional operation 614′ the effect of heat sink elements proximate the temperature sensitive structures is evaluated according to the method detailed in FIG. 6A, in order to provide a more realistic fully adjusted temperature that takes into account both the heating and cooling effects of structures proximate the temperature sensitive structures.

In some embodiments, in operation 616′ the adjusted temperature T′c, which takes into account cooling effects with regard to the temperature sensitive structure is used in running an EM evaluation to determine whether or not the integrated circuit design layout under evaluation satisfies the lifetime and performance goals for the particular design. For an integrated circuit design layout that passes the EM evaluation of operation 616′, in some embodiments, a tape out data file corresponding to the passing integrated circuit design layout is generated in optional operation 618′. For those integrated circuit design layouts for which a tape out data file is generated, the tape out data file will be used to manufacture a semiconductor device according to the passing integrated circuit design layout in optional operation 620′.

In some embodiments, the evaluation of the proximate structures includes identification of each of the structures proximate a heat sensitive structure as a heat generating structure, a heat sink element, or a neutral structure that forms a portion a transmission path for thermal coupling between the heat sensitive structure and the other structures and/or elements. In some embodiments, the temperature effects on the heat sensitive structure of both the proximate structures identified as heat generating structures and the proximate structures identified as heat sink elements are evaluated collectively to generate a fully adjusted temperature T″ that is then used in an EM evaluation.

In some embodiments according to a portion 700 of an integrated circuit design layout in FIG. 7A, a temperature sensitive structure, e.g., a target active region 702, is associated with a number of surrounding structures including additional active regions 708, 710, 712, 714, 716, 718, and 720, as well as conductive lines including metal zero M0 722, metal one M1 724, and metal two M2 726. In some embodiments, the identification of proximate structures will be based on an impact range 704 of X μm extending horizontally from the target active region 702 to define an impact area with the impact area, in turn, being projected vertically to define an impact volume.

An impact area 706 is defined as a horizontal region within the impact range of a periphery of the target active region. This impact area 706 is projected vertically, or rotated about a longitudinal axis of the target active region, to define an impact volume. The surrounding structures that fall within, or at least partially within, this impact volume have the potential to affect the target active region and are referred to as proximate structures. In some embodiments, each of these proximate structures are then, in turn, evaluated for identification as a heat generating structure or a heat sink element relative to the target active region. In some embodiments, the temperature difference between the estimated operating temperature of target active region 702 and a proximate structure must exceed a predetermined temperature difference before the proximate structure will be identified as a heat generating structure or a heat sink element.

In FIG. 7A, the active regions 708, 712, 716 exhibit a sufficient temperature difference and are used in calculating the adjusted and/or fully adjusted operating temperature of the target active region that will be used in the subsequent EM evaluation.

In some embodiments according to FIG. 7A, Eq. 4 is used for calculating the heat sink effects of proximate active regions, i.e., those active regions surrounding the target active region, or portions thereof, that are:

-   -   within an impact range X of the periphery of the target active         region;     -   are thermally coupled to the target active region through one or         more intervening layers or materials; and     -   are sufficiently “cold,” i.e., have a projected operating         temperature that is at least a predetermined value (° C.) or         percentage below the projected operating temperature of the         target active region.         ΔT _(ch_p_FE) =f(ΔT _(ch) ,RF         _(AR),Area_(proximate_AR),Area_(t_AR),Σ_AR, . . . )  [4]

ΔT_(ch): Original active region temperature without heat sink effect

ΔT_(ch_p_FE): active region temperature with front end (FE) heat sink(s) effects

Area_(t_AR): Target active region area

Area_(proximate_AR): Effective proximate connected-AR heat sink area

Σ_AR: Summation for (RF_(AR)*Area_(proximate_AR)) for all proximate connected-AR

RF_(AR): Fitting factor for active region heat sink based on silicon results

In some embodiments according to a portion 700 of an integrated circuit design layout in FIG. 7B, a temperature sensitive structure, e.g., a target active region 702, is associated with a number of surrounding structures including additional active regions 708, 710, 712, 714, 716, 718, and 720, as well as conductive lines including metal zero (M0) 722, metal one (M1) 724, and metal (M2) 726. Unlike the embodiments reflected in FIG. 7A, which focused on the target active region for defining an impact range, in some embodiments according to FIG. 7B, the identification of proximate structures is based on an impact range specific to each of the surrounding structures relative to the target active region 702. Accordingly, those proximate structures that exhibit a greater temperature difference relative to the target active region 702 (or which are separated from the target active region by more thermally conductive material(s)) have a correspondingly greater impact range than other proximate structures. As shown in FIG. 7B, active region 708 has a horizontal impact range of Z₁ μm 726 defining an impact area 728, active region 712 has a horizontal impact range of Z₂ μm 730 defining an impact area 732, and active region 716 has a horizontal impact range of Z₃ μm 734 defining an impact area 736.

In some embodiments according to FIG. 7B, the impact areas 728, 732, and 736 are used for identifying as proximate structures those of the surrounding structures which have a horizontal impact range that encompasses at least a portion of the target active region 702. In some embodiments, the temperature difference between the estimated operating temperature of target active region 702 and a proximate structure must exceed a predetermined level before the proximate structure will be identified as a heat generating structure or a heat sink element.

In FIG. 7B, the active regions 708, 712, 716 exhibit both a temperature difference exceeding the predetermined level and an impact area that overlaps a portion of target active region 702 and will be used in calculating the adjusted and/or fully adjusted operating temperature of the target active region that will be used in the subsequent EM evaluation.

In some embodiments according to FIG. 7B, Eq. 5 is used for calculating the heat sink effects of proximate active regions, i.e., those active region surrounding the target active region, or portions thereof, that are:

-   -   within an impact range Z of the periphery of each proximate         active region;     -   are thermally coupled to the target active region through one or         more intervening layers or materials; and     -   are sufficiently “cold,” i.e., have a projected operating         temperature that is at least a predetermined value (° C.) or         percentage below the projected operating temperature of the         target active region.         ΔT _(ch_p_FE) =f(ΔT _(ch),_(AR) RF         _(AR),Area_(proximate_AR),Area_(t_AR),Σ_AR, . . . )  [5]

ΔT_(ch): Original active region temperature without heat sink effect

ΔT_(ch_p_FE): active region temperature with front end (FE) heat sink effect(s)

Area_(t_AR): Target active region area

Area_(proximate_AR): Effective proximate connected AR heat sink area

Σ_AR: Summation for (RF_(AR)*Area_(proximate_AR)) for all proximate connected-active regions

RF_(AR): Fitting factor for active region heat sink based on silicon results

In addition to proximate active regions, a target active region will be impacted by the proximity of one or more back end (BE) or back end of line (BEOL) structures, particularly conductive lines, which exhibit greater thermal conductivity than the insulating materials surrounding and separating the target active region and proximate active region. In some embodiments, heat sink equation, Eq. 6, will be used for identifying and determining the contribution (if any) of proximate BE structures (conductive lines) to the operating temperature of the target active region. Proximate BE structures are those BE structures that are within an impact distance of the target active region and are thermally coupled to the target active region. In some embodiments, a final active region temperature will be calculated using Eq. 7, with the ΔT_(ch_p) being a function of the initial target active region temperature (which incorporates SHE and thermal coupling to other structures), heat sink effects attributable to FE structures, and heat sink effects attributable to BE structures. ΔT _(ch_p_BE) =f(ΔT _(ch) ,RF _(m),Area_(m),Area_(t_AR),Σ_m, . . . )  [6] ΔT _(ch_p) =f(ΔT _(ch) ,ΔT _(ch_p_FE) ,ΔT _(ch_p_BE))  [7]

ΔT_(ch): Original active region temperature without heat sink effect

ΔT_(ch_p): active region temperature with both heat sink effects

ΔT_(ch_p_FE): active region temperature with FE heat sink effects

ΔT_(ch_p_BE): active region temperature with BE heat sink effects

Area_(t_AR): Target active region area

Area_(m): Effective metal heat sink area for metal layer (m)

Σ_m: Summation for (RF_(m)*Area_(m)) for M0˜MX

RF_(m): Fitting factor for metal heat sink based on silicon results

Taking SHE into consideration during an EM evaluation, for example, helps to prevent an integrated circuit design layout from being characterized as more resistant to EM effects than the corresponding semiconductor device will actually achieve in operation, thereby helping to prevent unforeseen and premature field failures of the semiconductor devices. Considering only SHE; however, produces a worst-case scenario for the evaluation. In some integrated circuit design layouts, other nearby or proximate structures will provide a heat sink functionality that will mitigate the SHE, provide a more accurate estimation of the operating temperature of temperature sensitive structures, and reduce the need for unnecessary redesign(s) to improve the thermal performance of the resulting semiconductor devices.

Accordingly, an EM signoff methodology that takes into account both SHE and heat-sink effects with regard to temperature sensitive structures and/or functions helps to improve the accuracy of the integrated circuit design layout analysis. By improving the accuracy of the integrated circuit design layout analysis, embodiments of the methods will increase the confidence that semiconductor devices manufactured according to a particular integrated circuit design layout will perform as desired and maintain satisfactory performance for over the design lifetime of the semiconductor device.

The efficiency of EM signoff methodologies considering the thermal effects of a particular integrated circuit design layout is improved by utilizing equation-based thermal evaluations, thereby avoiding slower, more time-consuming and computational resource-consuming thermal modeling. The efficiency of some embodiments of the signoff methodologies are further improved by utilizing a pseudo-three-dimensional model for evaluating thermal coupling between various components including both front end of line (FEOL) and back end of line (BEOL) structures.

In some embodiments, the BE structures, particularly the conductive lines, are a focus of the EM evaluations. In some embodiments, the EM tool used for generating a final conductive line temperature will determine the final T_(metal) by factoring in both the environmental temperature T_(env) (or initial temperature T₀) and a calculated ΔT_(Metal) according to Eq. 8. In some embodiments, the final T_(metal) will then be evaluated using a temperature rating factor provided by the foundry or obtained from another source. In some embodiments, the temperature rating factor will be associated with a particular integrated circuit design layout while in other embodiments, the temperature rating factor will be associated with a particular manufacturing process that will be used to produce semiconductor devices. In general, the higher the value of the final T_(metal) (or, more broadly, a nominal temperature T_(nom)), the lower the temperature rating factor that a particular design will receive. T _(metal) =T _(env) +ΔT _(Metal)  [8] In some embodiments, the EM methodologies detailed above will be applied to any integrated circuit design layout and/or semiconductor manufacturing process in which SHE are anticipated to be a factor. In some embodiments, the integrated circuit design layouts will include FinFET devices and/or other planar or more complex structural semiconductor manufacturing processes.

In some embodiments, the self-heating aware EM evaluation identifies those regions, if any, of the integrated circuit design layout in which the SHE result in localized heating, e.g., a “hotspot,” that will reduce the overall EM performance and/or lifetime of semiconductor devices manufactured according to the integrated circuit design. In some embodiments, the initial self-heating aware EM evaluation is coupled with a heat sink-aware EM evaluation in order to determine if one or more surrounding structures is capable of mitigating the self-heating effects and/or thermal coupling effects previously identified and thereby improving the EM performance of the integrated circuit design layout.

In some embodiments, executing a heat sink-aware EM evaluation utilizes an electronic design automation (EDA) (also referred to as electronic computer-aided design (ECAD)) tool for identifying potential heat sink structures with in the integrated circuit design layout. In some embodiments, the EDA tool is configured to identify potential hotspots and heat sink structures from an integrated circuit design layout database (DB). Potential heat sink structures include, for example, active regions, guard rings, conductive lines, vias, and other structures that are located within a predetermined impact range of an identified hotspot or temperature sensitive structure. In some embodiments, the integrated circuit design layout DB will utilize Open Artwork System Interchange Standard (OASIS) or another language for representing the integrated circuit design layout.

In some embodiments, evaluation of potential heat sink structures will include consideration of parameters including, for example, structural dimensions, material properties, intervening materials, environmental conditions, and anticipated (calculated) operating temperatures. In some embodiments, an EDA tool is configured for calculating the total heat sink effect attributable to the identified heat sink structures and providing a temperature adjustment (reduction) for the temperature of the hotspot. In some embodiments, an EDA tool will utilize the temperature adjustment in determining the EM performance of the integrated circuit design layout.

In some embodiments, the heat sink aware EM sign-off methodology will provide more accurate local temperature calculations inside the integrated circuit design layout; more accurate thermal-aware EM evaluation results during the design phase; a reduced risk of premature product failure and/or overdesign; reduced simulation runtime using equation-based device temperature calculations; and reduced EM emulation runtime using pseudo-3D thermal models rather than full 3-D thermal modeling.

In some embodiments, BE structures, particularly conductive lines and vias, will act as heat sinks for temperature sensitive FE structures, e.g., an active region. In some embodiments according to the cross-section of a portion 800 of an integrated circuit design layout in FIG. 8, the target active region 802 has an impact range 810 and is connected to a conductive pattern M0 806 through via/contact 804. The conductive pattern M0 is, in turn, connected to conductive pattern M1 810 through via 808, conductive pattern M1 is connected to conductive pattern M2 814 through via 812. Conductive pattern M2 is connected to upper conductive patterns through via 816. Each of the conductive patterns is separated by ILD material 820. A top conductive pattern MX 818 is connected to lower conductive patterns through via 816′.

The impact range 810 will be used, in turn, to define an impact area (or impact window) 822 that incorporates the target active region and a surrounding region within X μm from the target active region 802. The impact area 822 will be used, in turn, to define an impact volume 824 the will contain at least portions of the proximate structures. In some embodiments, each of the conductive patterns 806, 810, 814, 818, will have a corresponding portion located within the impact volume 824 with the corresponding portion having a corresponding area AREA_(M0), AREA_(M1), AREA_(M2), AREA_(MX). Each of the portions of the conductive patterns that fall within an impact window defined by extending the impact range 810 from the periphery of the target active region will have a corresponding length, area, volume, and T_(metal) that will determine a degree of heat sink activity with respect to the target active region.

FIGS. 9A-D, are perspective views of a transformation of the results of EM evaluations conducted according to some embodiments using different techniques and/or methodologies. FIG. 9A is a base EM evaluation that does not include consideration of any heat sink impact and, as a result, exhibits a hotspot near the center of the integrated circuit design. FIG. 9B is the result of an EM evaluation that compensates for the presence of a guard ring (a front end of line (FEOL) heat sink structure) and reflects a reduction in the temperature of the hotspot found in FIG. 9A. FIG. 9C is the result of an EM evaluation that compensates for the presence of a conductive (metal) pattern above the active regions (a back end of line (BEOL) heat sink structure) and reflects a reduction in the temperature of the hotspot found in FIG. 9A. FIG. 9D is the result of an EM evaluation that compensates for both the presence of both a guard ring and conductive patterns (conductive lines) above the active regions (both FEOL and BEOL heat sink structures) and reflects an even greater reduction in the temperature of the hotspot found in FIG. 9A than the results in FIG. 9B or FIG. 9C.

FIG. 10 is a table including a transformation of the results of EM evaluations conducted according to some embodiments that include a heat sink analysis in the process of calculating a ΔT for illustrated features on a portion of an integrated circuit design layout. As reflected in FIG. 10, the heat sink structure(s) proximate the heat sensitive structure reduce the calculated ΔT of the heat sensitive structure by 2.4° C. (reduced from 12° C. to 9.6° C.) when compared to the ΔT value obtained without considering the effect(s) of the heat sink structure(s). The reduction in the ΔT will, in turn, improves the EM evaluation results for the integrated circuit design layout.

FIG. 11 is a block diagram of an electronic process control (EPC) system 1100, in accordance with some embodiments. Methods described herein of generating cell layout diagrams, in accordance with one or more embodiments, are implementable, for example, using EPC system 1100, in accordance with some embodiments. In some embodiments, EPC system 1100 is a general purpose computing device including a hardware processor 1102 and a non-transitory, computer-readable storage medium 1104. Storage medium 1104, amongst other things, is encoded with, i.e., stores, computer program code (or instructions) 1106, i.e., a set of executable instructions. Execution of computer program code 1106 by hardware processor 1102 represents (at least in part) an EPC tool which implements a portion or all of, e.g., the methods described herein in accordance with one or more (hereinafter, the noted processes and/or methods).

Hardware processor 1102 is electrically coupled to computer-readable storage medium 1104 via a bus 1118. Hardware processor 1102 is also electrically coupled to an I/O interface 1112 by bus 1118. A network interface 1114 is also electrically connected to hardware processor 1102 via bus 1118. Network interface 1114 is connected to a network 1116, so that hardware processor 1102 and computer-readable storage medium 1104 are capable of connecting to external elements via network 1116. Hardware processor 1102 is configured to execute computer program code 1106 encoded in computer-readable storage medium 1104 in order to cause EPC system 1100 to be usable for performing a portion or all of the noted processes and/or methods. In one or more embodiments, hardware processor 1102 is a central processing unit (CPU), a multi-processor, a distributed processing system, an application specific integrated circuit (ASIC), and/or a suitable processing unit.

In one or more embodiments, computer-readable storage medium 1104 is an electronic, magnetic, optical, electromagnetic, infrared, and/or a semiconductor system (or apparatus or device). For example, computer-readable storage medium 1104 includes a semiconductor or solid-state memory, a magnetic tape, a removable computer diskette, a random access memory (RAM), a read-only memory (ROM), a rigid magnetic disk, and/or an optical disk. In one or more embodiments using optical disks, computer-readable storage medium 1104 includes a compact disk-read only memory (CD-ROM), a compact disk-read/write (CD-R/W), and/or a digital video disc (DVD).

In one or more embodiments, storage medium 1104 stores computer program code 1106 configured to cause EPC system 1100 (where such execution represents (at least in part) the EPC tool) to be usable for performing a portion or all of the noted processes and/or methods. In one or more embodiments, storage medium 1104 also stores information which facilitates performing a portion or all of the noted processes and/or methods. In one or more embodiments, storage medium 1104 stores process control data 1108 including, in some embodiments, control algorithms, process variables and constants, target ranges, set points, and code for enabling statistical process control (SPC) and/or model predictive control (MPC) based control of the various processes.

EPC system 1100 includes I/O interface 1112. I/O interface 1112 is coupled to external circuitry. In one or more embodiments, I/O interface 1112 includes a keyboard, keypad, mouse, trackball, trackpad, touchscreen, and/or cursor direction keys for communicating information and commands to hardware processor 1102.

EPC system 1100 also includes network interface 1114 coupled to hardware processor 1102. Network interface 1114 allows EPC system 1100 to communicate with network 1116, to which one or more other computer systems are connected. Network interface 1114 includes wireless network interfaces such as BLUETOOTH, WIFI, WIMAX, GPRS, or WCDMA; or wired network interfaces such as ETHERNET, USB, or IEEE-1364. In one or more embodiments, a portion or all of noted processes and/or methods, is implemented in two or more EPC systems 1100.

EPC system 1100 is configured to receive information through I/O interface 1112. The information received through I/O interface 1112 includes one or more of instructions, data, design rules, process performance histories, target ranges, set points, and/or other parameters for processing by hardware processor 1102. The information is transferred to hardware processor 1102 via bus 1118. EPC system 1100 is configured to receive information related to a user interface (UI) through I/O interface 1112. The information is stored in computer-readable medium 1104 as user interface (UI) 1110.

In some embodiments, a portion or all of the noted processes and/or methods is implemented as a standalone software application for execution by a processor. In some embodiments, a portion or all of the noted processes and/or methods is implemented as a software application that is a part of an additional software application. In some embodiments, a portion or all of the noted processes and/or methods is implemented as a plug-in to a software application. In some embodiments, at least one of the noted processes and/or methods is implemented as a software application that is a portion of an EPC tool. In some embodiments, a portion or all of the noted processes and/or methods is implemented as a software application that is used by EPC system 1100.

In some embodiments, the processes are realized as functions of a program stored in a non-transitory computer readable recording medium. Examples of a non-transitory computer readable recording medium include, but are not limited to, external/removable and/or internal/built-in storage or memory unit, e.g., one or more of an optical disk, such as a DVD, a magnetic disk, such as a hard disk, a semiconductor memory, such as a ROM, a RAM, a memory card, and the like.

In some embodiments, methods for evaluating a heat sensitive structure of an integrated circuit design layout will be performed by one or more processors and will utilize operations including identifying a heat sensitive structure in the integrated circuit design, the heat sensitive structure having a nominal temperature T_(nom), identifying a first heat generating structure within a thermal coupling volume or range of the heat sensitive structure, calculating an operating temperature T_(oph1) of the first heat generating structure, calculating a temperature increase ΔT_(h1) for the heat sensitive structure induced by thermal coupling to the heat generating structure at the operating temperature T_(oph1), and conducting an evaluation of the heat sensitive structure at an evaluation temperature T_(E)=T_(nom)+ΔT_(h). Some embodiments of the method will also include the additional operations of identifying a second heat generating structure within a thermal coupling volume or range of the heat sensitive structure, calculating an operating temperature T_(oph2) for the second heat generating structure, calculating a ΔT_(h2) for the heat sensitive structure induced by thermal coupling to the second heat generating structure at the operating temperature T_(oph2), and conducting the evaluation of the heat sensitive structure at the evaluation temperature T_(E)=T_(nom)+ΔT_(h1)+ΔT_(h2).

In some embodiments, the heat sensitive structure is a conductive line and the evaluation comprises an electromigration analysis of the conductive line. In some embodiments, the first heat generating structure is a FinFET structure, the second heat generating structure is a high-resistance (Hi-R) structure, and/or another non-metallic structure. Some embodiments of the method will also include the additional operations of retrieving the integrated circuit design from a database of integrated circuit designs, generating a pseudo-3D model of the integrated circuit design, and/or retrieving thermal coupling data for the integrated circuit design.

In some embodiments, methods for evaluating a heat sensitive structure of an integrated circuit design layout will utilize operations including identifying a heat sensitive structure, calculating a nominal temperature T_(nom), identifying a first heat dissipating structure within a first thermal coupling volume or range of the heat sensitive structure, calculating an operating temperature Topc1 of the heat dissipating structure, calculating a ΔT_(c) for the heat sensitive structure induced by thermal coupling with the T_(opc1) of the heat dissipating structure, and conducting a performance evaluation of the heat sensitive structure at an evaluation temperature T_(E)=T_(nom)+ΔT_(c1). Some embodiments of the method will also include the additional operations of identifying a second heat dissipating structure within a second thermal coupling range of the heat sensitive structure, calculating an operating temperature T_(opc2) for the second heat dissipating structure, calculating a ΔT_(c2) for the heat sensitive structure induced by thermal coupling to the second heat dissipating structure at the operating temperature T_(opc2), and conducting the evaluation of the heat sensitive structure at the evaluation temperature T_(E)=T_(nom)+ΔT_(c1)+ΔT_(c2).

In some embodiments, the heat sensitive structure is a FinFET device and conducting the performance evaluation comprises conducting a performance analysis of the FinFET device. In some embodiments, the first thermal coupling volume or range and the second thermal coupling volume or range are different. Some embodiments of the method will also include the additional operations of calculating the nominal temperature T_(nom) by analyzing a self-heating effect ΔT for the heat sensitive structure and environmental temperature conditions T_(env), with T_(nom)=T_(env)+ΔT. In some embodiments, the first heat dissipating structure is an oxide defined (OD) region or a portion of a metal pattern. Some embodiments of the method will also include the additional operations of retrieving design data corresponding to the integrated circuit design from a database of integrated circuit designs and analyzing the design data to identify the heat sensitive structure(s) and the first heat dissipating structure(s) within the integrated circuit design layout, identifying a plurality of conductive layers in the integrated circuit design, and retrieving a plurality of thermal coefficients associated with each of the plurality of conductive layers, wherein the thermal coefficients comprise a de-rating coefficient, a layer effect, and a temperature profile.

In some embodiments, methods for evaluating a heat sensitive structure of an integrated circuit design will include the operations of identifying a heat sensitive structure having a nominal temperature T_(nom), identifying a first heat generating structure within a first thermal coupling range of the heat sensitive structure, calculating an operating temperature T_(oph) of the heat generating structure, calculating a ΔT_(h) for the heat sensitive structure induced by thermal coupling with the heat generating structure, identifying a heat dissipating structure within a second thermal coupling range of the heat sensitive structure, calculating an operating temperature T_(opc) of the heat dissipating structure, calculating a ΔT_(c) for the heat sensitive structure induced by thermal coupling with the heat dissipating structure; and conducting an evaluation of the heat sensitive structure at an adjusted temperature T_(E)=T_(nom)+ΔT_(h)+ΔT_(c). In some embodiments, the evaluation will include an electromigration and/or a performance analysis. Some embodiments of the method will also include the additional operations of determining whether the integrated circuit design passes the evaluation(s) and, if the integrated circuit design passes the evaluations, will generate a new tape out file that will be used for manufacturing a semiconductor device according to the integrated circuit design.

The present disclosure provides embodiments of methods for improving EM signoff methodologies in conjunction with the analysis of integrated circuit designs by taking into consideration both SHE and thermal coupling between heat generating structures, e.g., FinFET devices, and temperature sensitive structures, i.e., conductive lines to provide more accurate estimates of the performance and lifetime of semiconductor devices manufactured according to such integrated circuit designs. Although the subject matter has been described in terms of exemplary embodiments, it is not limited thereto. Rather, the appended claims should be construed broadly, to include other variants and embodiments, which may be made by those skilled in the art.

The foregoing outlines features of several embodiments so that those skilled in the art may better understand the aspects of the present disclosure. Those skilled in the art should appreciate that they may readily use the present disclosure as a basis for designing or modifying other processes and structures for carrying out the same purposes and/or achieving the same advantages of the embodiments introduced herein. Those skilled in the art should also realize that such equivalent constructions do not depart from the spirit and scope of the present disclosure, and that they may make various changes, substitutions, and alterations herein without departing from the spirit and scope of the present disclosure. 

The invention claimed is:
 1. A method for evaluating a heat sensitive structure comprising: identifying a heat sensitive structure in an integrated circuit design layout, the heat sensitive structure having a nominal operating temperature T_(nom); calculating a nominal operating temperature increase ΔT_(h1) for the heat sensitive structure induced by thermal coupling, within a thermal coupling volume, between a first heat generating structure at a nominal operating temperature T_(oph1) and the heat sensitive structure; and evaluating a functional parameter of the heat sensitive structure at an evaluation temperature T_(E)=T_(nom)+ΔT_(h1).
 2. The method according to claim 1, further comprising: calculating a nominal operating temperature increase ΔT_(h2) for the heat sensitive structure induced by thermal coupling, within the thermal coupling volume, between a second heat generating structure at a nominal operating temperature T_(oph2) and the heat sensitive structure; and evaluating the heat sensitive structure at the evaluation temperature T_(E)=T_(nom)+ΔT_(h1)+ΔT_(h2).
 3. The method according to claim 1, further comprising: identifying a conductive line as the heat sensitive structure; and evaluating the heat sensitive structure comprises an electromigration analysis of the conductive line.
 4. The method according to claim 1, further comprising: identifying a FinFET structure as the first heat generating structure.
 5. The method according to claim 2, further comprising: identifying a high-resistance (Hi-R) structure as the second heat generating structure is.
 6. The method according to claim 2, further comprising: identifying a non-metallic structure as the second heat generating structure.
 7. The method according to claim 2, further comprising: calculating a nominal operating temperature decrease ΔT_(c1) for the heat sensitive structure induced by thermal coupling, within the thermal coupling volume, between a first heat sink structure at a nominal operating temperature T_(opc1) and the heat sensitive structure; and evaluating the heat sensitive structure at the evaluation temperature T_(E)=T_(nom)+ΔT_(h1)+ΔT_(h2)ΔT_(c1).
 8. The method according to claim 1, further comprising: verifying that the heat sensitive structure passes the evaluation; and manufacturing a semiconductor device according to the integrated circuit design layout.
 9. A method for evaluating a heat sensitive structure of an integrated circuit design comprising: identifying the heat sensitive structure; calculating a nominal operating temperature T_(nom) of the heat sensitive structure with a first test program applied to the integrated circuit design; identifying a first heat dissipating structure within a first thermal coupling volume of the heat sensitive structure; calculating a nominal operating temperature T_(opc1) of the heat dissipating structure with the first test program applied to the integrated circuit design; calculating a ΔT_(c1) for the heat sensitive structure induced by thermal coupling between the heat dissipating structure at the nominal operating temperature T_(opc1) and the heat sensitive structure at the nominal operating temperature T_(nom); and conducting a performance evaluation of the heat sensitive structure at an evaluation temperature of at least T_(E)=T_(nom)ΔT_(c1).
 10. The method according to claim 9, further comprising: identifying a second heat dissipating structure within a second thermal coupling volume of the heat sensitive structure; calculating an operating temperature T_(opc2) for the second heat dissipating structure; calculating a ΔT_(c2) for the heat sensitive structure induced by thermal coupling to the second heat dissipating structure at the operating temperature T_(opc2); and conducting the evaluation of the heat sensitive structure at the evaluation temperature T_(E)=T_(nom)+ΔT_(c1)+ΔT_(c2).
 11. The method according to claim 9, further comprising: identifying a FinFET device as the heat sensitive structure; and conducting the performance evaluation comprises conducting a performance analysis of the FinFET device.
 12. The method according to claim 10, further comprising: defining the first thermal coupling volume; and defining the second thermal coupling volume; wherein the first and second thermal coupling volumes are unequal.
 13. The method according to claim 10, wherein: calculating the nominal temperature T_(nom) comprises an analysis of self-heating effect ΔT for the heat sensitive structure and environmental temperature conditions T_(env), with T_(nom)=T_(env)+ΔT.
 14. The method for evaluating a heat sensitive structure of an integrated circuit design according to claim 9, further comprising: identifying an active region as the first heat dissipating structure.
 15. The method according to claim 9, further comprising: identifying a portion of a metal pattern as the first heat dissipating structure.
 16. The method according to claim 9, further comprising: retrieving design data corresponding to the integrated circuit design from a database of integrated circuit designs; and analyzing the design data to identify the heat sensitive structure and the first heat dissipating structure.
 17. The method according to claim 10, further comprising: identifying a plurality of conductive layers in the integrated circuit design; and retrieving a plurality of thermal coefficients associated with each of the plurality of conductive layers, wherein the thermal coefficients comprise a de-rating coefficient, a layer effect, and a temperature profile.
 18. A method for evaluating a heat sensitive structure of an integrated circuit design comprising: identifying a heat sensitive structure having a nominal temperature T_(nom); performing a pseudo 3-D analysis of any structures and materials encompassing the heat sensitive structure to define a first thermal coupling volume; identifying a first heat generating structure within the first thermal coupling volume of the heat sensitive structure; calculating an operating temperature T_(oph) of the heat generating structure; calculating a ΔT_(h) for the heat sensitive structure induced by thermal coupling with the heat generating structure; identifying a heat dissipating structure within the first thermal coupling volume of the heat sensitive structure; calculating an operating temperature T_(opc) of the heat dissipating structure; calculating a ΔT_(c) for the heat sensitive structure induced by thermal coupling with the heat dissipating structure; conducting an evaluation of the heat sensitive structure at an adjusted temperature T_(E)=T_(nom)+ΔT_(h)+ΔT_(c); and generating tape out data for the production of a mask set after the heat sensitive structure passes the evaluation.
 19. The method according to claim 18, further comprising: conducting an electromigration analysis as the evaluation of the heat sensitive structure.
 20. The method according to claim 19, further comprising: determining whether the integrated circuit design passes the electromigration analysis and, if the integrated circuit design passes, generating a new tape out file for manufacture of a semiconductor device according to the integrated circuit design. 